Four-fixed-end-beam type wireless vibration sensor based on surface acoustic waves

Abstract

The invention discloses a four-fixed-end-beam wireless vibration sensor based on surface acoustic waves, which is provided with four piezoelectric fixed end beams, the four piezoelectric fixed end beams are symmetrically distributed at the left and right ends of the upper and lower surfaces of a mass block respectively, and the inner end, namely the stress end, of each piezoelectric fixed end beam is fixedly connected to the surface of the mass block. The outer end, namely the fixed end, extends outwards along the surface where the fixed end is located and then is fixed; the supporting block is fixedly connected between the cross beam and the mass block to limit the position of the mass block, so that the vibration of the mass block is within a preset range; the fixed end of each piezoelectric fixed end beam is fixed by being fixedly connected to the corresponding frame; each piezoelectric fixed end beam extending outwards is fixedly connected with a modulation circuit board, and the modulation circuit board is provided with an antenna. The wireless piezoelectric sensor has the advantages of being higher in monitoring efficiency, high in axial vibration signal monitoring accuracy, stable in piezoelectric effect, small in size, light in weight, low in power consumption, low in cost and high in stability.

Description

Technical Field

[0001] The present invention relates to the technical field of surface acoustic wave sensors, and particularly relates to a four-fixed-end beam type wireless vibration sensor based on surface acoustic waves. Background Art

[0002] In the industrial field, it is crucial to monitor the health status of mechanical components in motion in real time. For example, monitoring the vibration state of the doors of high-speed rail vehicles or the vibration of the automobile chassis. This health monitoring method can replace the traditional regular maintenance strategy, significantly reducing the time cost and maintenance operation cost. By introducing wireless passive and miniaturized sensor technologies, continuous monitoring can be achieved in dangerous environments, improving the safety and convenience of monitoring, and at the same time avoiding the problem of complex wiring of traditional wired sensors.

[0003] Sensors based on surface acoustic wave (SAW) technology have the advantages of small size, wireless passivity, and fast response speed, and are particularly suitable for applications in harsh environments. In addition, its wireless passive characteristic greatly improves the safety and reliability of the system.

[0004] Surface acoustic wave devices mainly include two structural forms: delay line type and resonant type, and are suitable for detecting physical quantities such as pressure, temperature, acceleration, and vibration. Compared with the resonant type, the delay line type structure is simpler, has a lower manufacturing cost, and can integrate the identity recognition and sensing functions in the same device. Therefore, it has better economy and flexibility in practical applications. The present invention is designed based on the delay line type structure, further improving the integration and practicality of the device.

[0005] The working principle of wireless passive surface acoustic wave vibration sensing technology is as follows: The interdigital transducer (IDT) receives a query pulse signal from the control system through the antenna and converts it into a surface acoustic wave propagating along the surface of the piezoelectric crystal. During the propagation process, the surface acoustic wave is reflected by the reflector, and then is converted into an electromagnetic wave signal by the interdigital transducer again and transmitted to the external device through the antenna. When vibration occurs in the external environment, the mass block causes a certain degree of bending deformation of the cantilever beam with the change of acceleration, thereby causing a change in the acoustic wave signal. This change can be used to characterize the vibration intensity signal. It should be noted that during the signal propagation process, it is easily affected by the external environment, and there may be cross-interference between signals. These interferences will directly affect the intensity and speed of signal transmission, thereby reducing the detection accuracy and reliability of the sensor.

[0006] A wireless passive surface acoustic wave vibration sensor disclosed in the prior art with the publication number CN107238431A realizes compensation for acoustic wave propagation attenuation by optimizing the SAW device. In this solution, the structure of the sensor is not optimized, so the above problems still exist. Summary of the Invention

[0007] 1. Technical problem to be solved: In view of the above technical problems, the present invention provides a four-fixed-end beam type wireless vibration sensor based on surface acoustic wave, which not only solves the problems such as inconvenient multi-point monitoring in practical applications due to the connection method of wired piezoelectric sensors, but also aims at the problem that when the existing wireless piezoelectric sensors monitor axial vibration data, they are greatly affected by the horizontal direction, resulting in insufficient data accuracy.

[0008] 2. Technical solution: A four-fixed-end beam type wireless vibration sensor based on surface acoustic wave, characterized in that: it is provided with four piezoelectric fixed-end beams, and the four piezoelectric fixed-end beams are symmetrically distributed at the left and right ends of the upper and lower surfaces of the mass block respectively. The inner end, i.e., the force-receiving end, of each piezoelectric fixed-end beam is fixedly connected to the surface of the mass block, and its outer end, i.e., the fixed end, extends outward along the surface where it is located and then is fixed.

[0009] Furthermore, it further includes a silicon frame, a support block, a PCB modulation circuit, an antenna and a wireless data control system; the silicon frame includes a frame surrounding the mass block in a distance from the ground and a cross beam in the front-back direction across the upper and lower surfaces of the mass block; the support block is fixedly connected between the cross beam and the mass block to limit the position of the mass block, so that the vibration of the mass block is within a preset range; the fixed end of each piezoelectric fixed-end beam is fixed through fixed connection to the corresponding frame; each outward-extending piezoelectric fixed-end beam is fixedly connected to a PCB modulation circuit board, and an antenna is provided on the PCB modulation circuit board; the wireless piezoelectric sensor is communicatively connected to the wireless data control system through the antenna.

[0010] Furthermore, the piezoelectric fixed-end beam is formed by a short-circuit reflection grating and a SAW filter respectively deposited on the surface of the elastic plate from the inside to the outside through semiconductor technology; the SAW filter is composed of an interdigital transducer and a piezoelectric substrate; the short-circuit reflection gratings and SAW filters of the two piezoelectric fixed-end beams fixed on the same mass block surface are symmetrically arranged with the support block as the center; the horizontal distance between two adjacent piezoelectric fixed beams is 6-8 mm, and the vertical distance is 2-3 mm.

[0011] Furthermore, the mass block is square; the frame of the silicon frame is square; the support block is square and its surface is smaller than that of the mass block, and the support block is fixed at the middle position of the mass block; the cross beam of the silicon frame has the same shape as the support block at the position corresponding to the support block.

[0012] Furthermore, the mass block is made of copper, aluminum or stainless steel, and its surface is coated with mineral fiber sound-absorbing paint.

[0013] Further, the size of the horizontal plane of the mass block is 12mm * 10mm, and the height is 3mm; the size of the horizontal plane of the silicon frame is 20mm x 20mm, and the height is 3mm; the size of the horizontal plane of the support block is 6mm * 6mm, and the height is 1.5mm.

[0014] Further, the support block is provided with a small unit honeycomb structure; the small unit honeycomb structures are distributed alternately vertically and horizontally, and the aperture size thereof is 0.4 - 0.8mm.

[0015] Further, the support block is made of aluminum alloy or carbon fiber composite material.

[0016] Further, the cantilever beam, the silicon frame and the mass block are all fixed by bonding.

[0017] Further, the piezoelectric substrate is an ST - quartz material substrate.

[0018] 3. Beneficial effects: (1) A four - fixed - end - beam - type wireless vibration sensor based on surface acoustic wave provided by this method improves the structure of the traditional wireless piezoelectric sensor. The sensor is provided with four fixed - end beams, and the force - receiving end of each fixed - end beam is connected to the mass block, which can effectively sense subtle vibrations and ensure the effective transmission of vibration responses. At the same time, the four cantilever beams are all connected to the same mass block by bonding, ensuring the same vibration pace and effectively reducing interference. The fixed end of the cantilever beam is connected to the silicon frame, and the force - receiving end is connected to the mass block, which can ensure the effective transmission of vibration responses.

[0019] (2) A four - fixed - end - beam - type wireless vibration sensor based on surface acoustic wave provided by this method adhesively fixes a support block on both the upper and lower surfaces of the mass block. The support block is provided with a small unit honeycomb structure (such as made of carbon fiber composite material), and the upper and lower surfaces are respectively connected to the silicon frame and the mass block. Since the small unit honeycomb structures are distributed alternately vertically and horizontally, the honeycomb structure has good support in the axial direction and provides support forces in different directions on the horizontal plane, thereby restricting the horizontal displacement of the mass block, ensuring its stable movement trajectory, and reducing the offset in the horizontal plane direction.

[0020] (3) A four - fixed - end - beam - type wireless vibration sensor based on surface acoustic wave provided by this method has a mass block made of materials such as copper, aluminum or stainless steel, and is coated with mineral fiber sound - absorbing coating to absorb surface acoustic waves and prevent them from penetrating the mass block and interfering with the devices on other cantilever beams.

[0021] In summary, the wireless piezoelectric sensor has the advantages of higher monitoring efficiency, high precision in monitoring axial vibration signals, stable piezoelectric effect, small size, light weight, low power consumption, low cost, and strong stability. It can achieve unattended and accurate monitoring in harsh environments and has broad application prospects. Brief Description of the Drawings

[0022] Figure 1 is an external view of a four-fixed-end beam type wireless vibration sensor based on surface acoustic wave of the present invention; Figure 2 is a sectional view of a four-fixed-end beam type wireless vibration sensor based on surface acoustic wave of the present invention; Figure 3 In the present invention Figure 1 is a schematic diagram of the surface circuit of the piezoelectric fixed-end beam in the upper right; Figure 4 is a schematic diagram of the support block and its small unit honeycomb structure of the present invention; Figure 5 is a schematic diagram of the connection between the piezoelectric fixed-end beam, the silicon frame, and the support block of the present invention.

[0023] Reference numerals: piezoelectric fixed-end beam 1; mass block 2; silicon frame 3; support block 4; PCB modulation circuit 5; antenna 6; wireless data control system 7; short-circuit reflection grating 8; elastic plate 10; interdigital transducer 11; piezoelectric substrate 12; small unit honeycomb structure 13. Detailed Description of the Invention

[0024] The present invention will be specifically described below with reference to the drawings.

[0025] As shown in Figure 1 to Figure 5 A four-fixed-end beam type wireless vibration sensor based on surface acoustic wave, characterized in that: it is provided with four piezoelectric fixed-end beams 1, and the four piezoelectric fixed-end beams are symmetrically distributed at the left and right ends of the upper and lower surfaces of the mass block respectively. The inner end, i.e., the force-receiving end, of each piezoelectric fixed-end beam is fixedly connected to the surface of the mass block 2, and its outer end, i.e., the fixed end, extends outward along the surface where it is located and then is fixed.

[0026] Further, it also includes a silicon frame 3, a support block 4, a PCB modulation circuit 5, an antenna 6, and a wireless data control system 7; the silicon frame includes a frame that surrounds the mass block at a distance in all directions and crossbeams in the front-back direction that span the upper and lower surfaces of the mass block; the support block is fixedly connected between the crossbeam and the mass block to limit the position of the mass block, so that the vibration of the mass block is within a preset range; the fixed end of each piezoelectric fixed-end beam is fixed by being fixedly connected to the corresponding frame; each piezoelectric fixed-end beam extending outward is fixedly connected to a PCB modulation circuit board, and an antenna is provided on the PCB modulation circuit board; the wireless piezoelectric sensor is communicatively connected to the wireless data control system through the antenna.

[0027] Further, the piezoelectric fixed-end beam is formed by a short-circuit reflection grating 8 and a SAW filter that are respectively deposited on the surface of the elastic plate 10 from the inside to the outside through semiconductor processes; the SAW filter is composed of an interdigital transducer 11 and a piezoelectric substrate 12; the short-circuit reflection gratings and SAW filters of the two piezoelectric fixed-end beams fixed on the same mass block surface are symmetrically arranged with the support block as the center; the horizontal distance between two adjacent piezoelectric fixed beams is 6-8 mm, and the vertical distance is 2-3 mm.

[0028] Further, the mass block is square; the frame of the silicon frame is square; the support block is square and its surface is smaller than that of the mass block, and the support block is fixed at the middle position of the mass block; the crossbeam of the silicon frame has the same shape as the support block at the position corresponding to the support block.

[0029] Further, the mass block is made of copper, aluminum, or stainless steel, and its surface is coated with mineral fiber sound-absorbing paint.

[0030] Further, the size of the horizontal plane of the mass block is 12 mm * 10 mm, and the height is 3 mm; the size of the horizontal plane of the silicon frame is 20 mm x 20 mm, and the height is 3 mm; the size of the horizontal plane of the support block is 6 mm * 6 mm, and the height is 1.5 mm.

[0031] Further, the support block is provided with a small unit honeycomb structure 13; the small unit honeycomb structures are distributed alternately vertically and horizontally, and the aperture size is 0.4-0.8 mm.

[0032] Further, the support block is made of aluminum alloy or carbon fiber composite material.

[0033] Further, the cantilever beam, the silicon frame, and the mass block are all fixedly connected by bonding.

[0034] Further, the piezoelectric substrate is a ST-quartz material substrate.

[0035] Working principle: As Figure 1 、2 As shown in FIGS. 3, the specific structure of a piezoelectric fixed-end beam in this method includes a short-circuit reflection grating and a SAW filter, and the specific arrangement order is as shown in the appendix Figure 3 As shown, from the inside out are a short-circuit reflection grating, a spacer, an interdigital transducer IDT, a spacer, a short-circuit reflection grating, a spacer, and a short-circuit reflection grating; the spacer in the figure is the white part.

[0036] As Figure 1 shown, when the sensor is vibrated, the mass block connected to one end of the piezoelectric cantilever beam generates a displacement along the direction of the applied force due to the action of the vibration acceleration, resulting in bending or torsional deformation. The change in the surface strain of the piezoelectric cantilever beam causes a change in the inherent properties of the signal on the SAW device. By decoupling the signal change through an algorithm, real-time sensing of the vibration quantity can be achieved.

[0037] In this solution, the outer surface of the mass block is coated with a mineral fiber sound-absorbing coating to absorb surface acoustic waves and prevent surface acoustic waves from penetrating the mass block and affecting the operation of the SAW filters on other cantilever beams, thereby improving the monitoring accuracy of the sensor. The antenna uses a microstrip antenna, which has the characteristics of smaller volume, lighter weight, and higher efficiency.

[0038] In this solution, the support block has a small-unit honeycomb structure, as shown in the appendix Figure 4 As shown, Figure 4 In the figure, the left figure is an enlarged schematic diagram of the structure of the small-unit honeycomb structure; the purpose of using the small-unit honeycomb structure in this solution is to limit the horizontal movement of the mass block, reduce the displacement deviating from the vertical center, and reduce signal interference. The small-unit honeycomb structures of the support block are distributed alternately vertically and horizontally to provide support forces in different directions on the horizontal plane. The aperture size of the small-unit honeycomb structure is fine-tuned according to the actual vibration situation.

[0039] Although the present invention has been disclosed above with preferred embodiments, they are not used to limit the present invention. Any person skilled in this art can make various changes or modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention should be defined by the protection scope of the claims of this application.

Claims

1. A four-fixed-end beam wireless vibration sensor based on surface acoustic wave, characterized in that: It is provided with four piezoelectric fixed end beams, which are symmetrically distributed at the left and right ends of the upper and lower surfaces of the mass block, respectively. The inner end, i.e., the force-bearing end, of each piezoelectric fixed end beam is fixedly connected to the surface of the mass block, and the outer end, i.e., the fixed end, extends outward along the surface on which it is located and then is fixed.

2. The four-fixed-end beam type wireless vibration sensor based on surface acoustic wave according to claim 1 is characterized in that: It also includes a silicon frame, a support block, a PCB modulation circuit, an antenna and a wireless data control system; the silicon frame includes a frame that surrounds the mass block at a distance and a beam that spans the front and rear directions of the upper and lower surfaces of the mass block; the support block is fixedly connected between the beam and the mass block to limit the position of the mass block, so that the vibration of the mass block is within a preset range; the fixed end of each piezoelectric fixed end beam is fixedly connected to the corresponding frame to achieve its fixation; each piezoelectric fixed end beam extending outward is fixedly connected to a PCB modulation circuit board, and an antenna is provided on the PCB modulation circuit board; the wireless piezoelectric sensor is connected to the wireless data control system for communication via the antenna.

3. The four-fixed-end beam type wireless vibration sensor based on surface acoustic wave according to claim 1, characterized in that: The piezoelectric fixed-end beam is composed of a short-circuit reflection grating and a SAW filter, which are deposited on the surface of the elastic plate from the inside to the outside through a semiconductor process; the SAW filter is composed of an interdigital transducer and a piezoelectric substrate; the short-circuit reflection grating and the SAW filter of the two piezoelectric fixed-end beams fixed on the surface of the same mass block are arranged symmetrically with the support block as the center; the horizontal distance between two adjacent piezoelectric fixed beams is 6~8mm, and the vertical distance is 2~3mm.

4. The four-fixed-end beam type wireless vibration sensor based on surface acoustic wave according to claim 2 is characterized in that: The mass block is square; the frame of the silicon frame is square; the support block is square and its surface is smaller than that of the mass block, and the support block is fixed at the middle position of the mass block; the crossbeam of the silicon frame corresponds to the position of the support block and its shape is the same as that of the support block.

5. The four-fixed-end beam type wireless vibration sensor based on surface acoustic wave according to claim 2, characterized in that: The mass block is made of copper, aluminum or stainless steel, and its surface is coated with mineral fiber sound-absorbing paint.

6. The four-fixed-end beam type wireless vibration sensor based on surface acoustic wave according to claim 4, characterized in that: The size of the horizontal plane of the mass block is 12mm*10mm, and the height is 3mm; the size of the horizontal plane of the silicon frame is 20mmx20mm, and the height is 3mm; the size of the horizontal plane of the support block is 6mm*6mm, and the height is 1.5mm.

7. The four-fixed-end beam type wireless vibration sensor based on surface acoustic wave according to claim 1, characterized in that: The support block is provided with a small unit honeycomb structure; the small unit honeycomb structure is alternately distributed vertically and horizontally, and the pore size thereof is 0.4-0.8 mm.

8. The four-fixed-end beam type wireless vibration sensor based on surface acoustic wave according to claim 1, characterized in that: The support block is made of aluminum alloy or carbon fiber composite material.

9. The four-fixed-end beam type wireless vibration sensor based on surface acoustic wave according to claim 2, characterized in that: The cantilever beam, the silicon frame and the mass block are all fixed by bonding.

10. The four-fixed-end beam type wireless vibration sensor based on surface acoustic wave according to claim 3, characterized in that: The piezoelectric substrate is a ST-quartz material substrate.

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